Distribution of basement membrane components in the mouse primary palate.

Laminin, type IV collagen, and fibronectin are major components of the basement membrane of epithelial tissues. The purpose of this study was to characterize their distributions as the epithelial seam of the primary palate is disrupted and the mesenchymal bridge forms and enlarges. The distributions of these molecules were studied with indirect immunofluorescence in day 11 (9-20 tail somites), noncleft CD1 mice. During epithelial seam formation at 9-11 tail somites (TS), all three molecules were intensely localized in the basement membrane of the seam and adjacent stomodeal and nasal epithelia. During epithelial seam replacement by mesenchymal tissues at 12-18 TS, basement membrane components were first fragmented along the seam, then absent at the site of the mesenchymal bridge. At 19-20 TS, basement membrane components were intact around the margins of the primary palate. These results show that disruption of basement membrane components occurs rapidly and simultaneously with mesenchymal bridge formation in the primary palate.